| 摘要 |
PROBLEM TO BE SOLVED: To provide a coordinate input device and a control method thereof and a program capable of precisely detecting coordinates with no error and superior in S/N even in a large scale.SOLUTION: The coordinate input device comprises: a light receiving part and plural light projection parts which are disposed at a corner of a coordinate input effective region; and a reflecting part disposed in a periphery area of the coordinate input effective region to recursively reflect incident light. The plural light projection parts are disposed with a predetermined distance from the light receiving part in a vertical direction with respect to the coordinate input effective region. The plural light projection parts are driven synchronously with the drive timing of the light receiving part. A threshold value is set at a level so that the rising portion and the falling part of a light-shielding portion included in a light quantity distribution obtained by the light receiving part are maintained symmetrically with respect to the center position between the two. An instruction position is calculated based on the pixel number corresponding to the center position between the rising portion and the falling part of the light-shielding portion corresponding to a point crossing at the threshold value with respect to the light quantity distribution. |
